//manages a deposit or withdrawal
 public string DepWith(string sType, string sUser, string sAmmount)
 {
     Customer myCustomer = new Customer();
     try
     {
         string sAccount = myCustomer.GetAccount(sUser);
         if (sType.Equals("WITHDRAW"))
             if (GetBalance(sAccount) < double.Parse(sAmmount)) return "0";
         return Create(sType, sAmmount, sAccount);
     }
     catch (Exception ex)
     {
         Console.WriteLine(ex.ToString());
         return "-1";
     }
 }
        //returns customer's balance (and customer account's turnover)
        public string Balance(string sUser, string sMode)
        {
            Customer myCustomer = new Customer();

            try
            {
                string sAccount = myCustomer.GetAccount(sUser);

                if (sMode.Equals("N"))
                    return "Current balance on your cash account is: " + GetBalance(sAccount).ToString();

                return "Current balance on your cash account is: " + GetBalance(sAccount).ToString() + "\n" + GetTurnover(sAccount);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
                return "-1";
            }
        }